Imaging device and driving method thereof

ABSTRACT

There is provided an imaging device which eliminates complexity in reading an image in low resolution and reading an image in high resolution and realizes prevention of decrease in frame rate. The device includes a pixel region including a plurality of pixel elements and imaging an incident light of an object as an image and a reading unit for thinning out a pixel element from the pixel region to read a thinned out image in low resolution and reading a partial image in resolution higher than the thinned out image from a partial region of the pixel region (a horizontal shift register and a vertical shift register), wherein the reading unit reads the thinned out image and the partial image from mutually different pixel elements and reads the thinned out image and the partial image as different imaging frames.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an imaging device which includes apixel region including a plurality of pixel elements and imaging anincident light of an object as an image and a driving method thereof.

2. Description of the Related Art

As a conventional imaging device capable of imaging a wide imaging areawith low resolution and imaging a predetermined partial imaging areawith high resolution, there is, for example, Japanese Patent ApplicationLaid-Open No. H09-214836 and Japanese Patent Application Laid-Open No.2000-032318.

In Japanese Patent Application Laid-Open No. H09-214836, an imagingdevice capable of reading data of a predetermined pixel element is used.And a block mode for reading only the pixel element of a predeterminedblock among all pixel elements, and a skip mode for reading all pixelelements at a predetermined thinning-out rate are switched to drive,write in memory and display. Thereby, an imaging device capable ofimplementing adjustment of angle of view prior to imaging and imagedisplay for focusing rapidly and accurately is provided. Moreover, animaging device capable of making a fully-displayed image on one displaywith short recurrence cycle and an image displayed in apartially-enlarged manner viewable at the same time is provided.

In addition, in Japanese Patent Application Laid-Open No. 2000-032318,an imaging device comprising a solid-state imaging device having atwo-dimensional pixel array and made to scan in a plurality of scanningmodes has been disclosed. This imaging device scans all pixel elementsonly of a pixel group of a continued predetermined region in the pixelarray of the solid-state imaging device. Moreover, this imaging devicecomprises a scan control unit scanning the pixel group in the remainingregion of the pixel array in a thinning out manner and a video signalseparating unit separating a video signal from the entire pixel scanningregion and a video signal from a thinning out scanning region eachother. Thereby, an imaging device capable of obtaining from the sameframe entire image information by thinning out scanning and highresolution partial image information by entire pixel scanning at thesame time is provided.

However, the above described two patent documents respectively includethe following problems. At first, the imaging device described inJapanese Patent Application Laid-Open No. H09-214836 uses the same pixelelement at the occasion of reading an image in low resolution andreading an image in high resolution. Therefore, also in the case ofreading a frame in low resolution and a frame in high resolutionalternately, accumulation and pixel reading have to be carried outchronologically for each frame to consequently reduce the effectiveframe rate, giving rise to a problem.

In addition, the imaging device described in Japanese Patent ApplicationLaid-Open No. 2000-032318 will obtain an image in low resolution and animage in high resolution from the same frame. Therefore, exposurecontrol or the gain of each pixel element has to be adjusted on eachimage and, therefore, change in driving timing of a sensor becomescomplicated, giving rise to a problem.

Moreover, both of the above described imaging devices are not consideredon the driving frequency at the time of image reading; a frame rate ofeach image will be change in the case where a plurality of images inhigh resolution are read, giving rise to a problem.

SUMMARY OF THE INVENTION

The present invention has been attained in view of the above describedproblems and an object thereof is to provide an imaging device capableof realizing prevention of decrease in frame rate without complicatingreading of an image in low resolution and an image in high resolutionand to provide a driving method thereof.

An imaging device of the present invention includes a pixel regionincluding a plurality of pixel elements and imaging an incident light ofan object as an image and a reading unit for thinning out a pixelelement from the pixel region to read a thinned out image in lowresolution and reading a partial image in resolution higher than thethinned out image from a partial region of the pixel region, wherein thereading unit reads the thinned out image and the partial image frommutually different pixel elements and reads the thinned out image andthe partial image as mutually different imaging frames. In addition animaging device of the present invention includes a pixel regionincluding a plurality of pixel elements and imaging an incident light asan image and a reading unit for thinning out a pixel element from thepixel region to read a thinned out image in low resolution and reading apartial image in resolution higher than the thinned out image from apartial region of the pixel region, wherein the reading unit reads thethinned out image and the partial image from mutually different pixelelements and reads in mutually different accumulation periods.

A method of driving an imaging device of the present invention is amethod of driving an imaging device which includes a pixel regionincluding a plurality of pixel elements and imaging an incident light ofan object as an image, wherein the method comprises steps of; readingout a thinned out image in low resolution by thinning out a pixelelement from the pixel region; and reading out a partial image from apartial region of the pixel region in higher resolution than theresolution of the thinned out image. During the two reading steps, thethinned out image and the partial image are read out from respectivelydifferent pixel elements, and from respectively different imaging frame.

According to the present invention, it is possible to realize preventionof decrease in frame rate without complicating reading of an image inlow resolution and an image in high resolution.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a schematic configurationof an imaging device related to an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating an example of an embodiedimage by the imaging device related to the embodiment of the presentinvention.

FIG. 3 is a schematic diagram of a pixel region illustrating an exampleof the embodied image by the imaging device related to the embodiment ofthe present invention.

FIG. 4 is a schematic diagram of a pixel region illustrating an exampleof an embodied image by the imaging device related to the embodiment ofthe present invention.

FIG. 5 is a schematic diagram of a pixel region illustrating the exampleof an embodied image by the imaging device related to the embodiment ofthe present invention.

FIG. 6 is a diagram illustrating an example of a circuit in a unit pixelelement of a pixel region enabling random access.

FIG. 7 is a diagram illustrating an example of a circuit in a unit pixelelement of a pixel region.

FIG. 8 is a diagram illustrating another example of a circuit in a pixelregion.

FIG. 9 is a diagram illustrating an example of a schematic configurationof a sensor unit (imaging device) of an imaging device related to anembodiment of the present invention.

FIG. 10 is a timing chart illustrating an example of a method of drivingan imaging device related to an embodiment of the present invention.

FIGS. 11A and 11B are timing charts illustrating an example of inputtiming of a reset pulse determining setting of an accumulation period ofa pixel element in a row 1.

FIG. 12 is a timing chart illustrating an embodiment of the presentinvention and illustrating an example of changing driving frequenciesfor reading a thinned out image in low resolution and for reading apartial image in high resolution.

DESCRIPTION OF THE EMBODIMENTS

With reference to the accompanying drawings, embodiments of the presentinvention will be described below.

FIG. 1 is a diagram illustrating an example of a schematic configurationof an imaging device related to an embodiment of the present invention.An imaging device 100 comprises, for example, an optical unit 110, asensor unit (imaging device) 120, a signal processing circuit unit 130,a recording and transmitting unit 140, a timing control circuit unit150, a system control circuit unit 160 and a reproducing and displayingunit 170.

An incident light of an object through the optical unit 110 is focusedon the sensor unit (imaging device) 120 to form an image. The sensorunit (imaging device) 120 includes, for example, a pixel region wherepixel elements are arranged in a two dimensional matrix. When theincident light of an object is focused in the pixel region to form animage, the light of an object is converted into an electrical signal(image signal) by each pixel element of the pixel region and an image isimaged.

The image signal converted in each pixel element of the sensor unit(imaging device) 120 undergoes signal conversion processing in apredetermined method in the signal processing circuit unit 130. And, theimage signal having undergone signal processing by the signal processingcircuit unit 130 is recorded by a recording medium, transmitted to anexternal apparatus by the recording and transmitting unit 140 or isdirectly sent to the reproducing and displaying unit 170 and isreproduced and displayed. In addition, the image signal recorded in arecording medium by the recording and transmitting unit 140 istransmitted to the reproducing and displaying unit 170 according tonecessity and is reproduced and displayed.

The timing control circuit unit 150 controls the driving timing for thesensor unit (imaging device) 120 and the signal processing circuit unit130 based on control by the system control circuit unit 160. The systemcontrol circuit unit 160 controls operation of the imaging devicesynthetically and controls respective component units of the opticalunit 110, the recording and transmitting unit 140, the timing controlcircuit unit 150 and the reproducing and displaying unit 170. Inaddition, the system control circuit unit 160 controls drive of thesensor unit (imaging device) 120 and the signal processing circuit unit130 through the timing control circuit unit 150.

Next, at first, the present invention will be described briefly. FIG. 2is a schematic diagram illustrating an example of an embodied image bythe imaging device related to the embodiment of the present invention.Here, FIG. 2 schematically illustrates relation between a pixel region121 provided in the sensor unit (imaging device) 120 and partial imagesA and B after being read from each pixel element of the pixel region 121and a thinned out image C. That is, FIG. 2 illustrates the pixels forthinned out image (C) and the pixels for partial images (A, B) amongpixel elements included in the pixel region 121.

As illustrated in FIG. 2, the entire image in the pixel region 121 isformed based on a small number of pixel signals read from the pixels forthinned out image (C). Here, the entire image is thinned out and readfrom the entire pixel region 121 and, therefore, will become an image inlow resolution. And, for example, the system control circuit unit 160controls recording of and monitors this entire image and determines anoticed image region to be noticed from the result of monitoringthereof. And, for example, the system control circuit unit 160 reads andbrings a small number of pixel signals in that noticed image region intosignal processing and, thereby, the partial image A and the partialimage B in high resolution are formed and undergo processingcorresponding with an object of monitoring.

In the present invention, the pixel elements utilized for the partialimages (A, B) will not be utilized as pixel elements utilized for thethinned out image (C). That is, in the case illustrated in FIG. 2, inthe pixel regions of the partial images (A, B), the pixel signals fromthe pixels for thinned out image (C) will not be read at the time ofreading the relevant partial images (A, B).

The timing control circuit unit 150 drives the pixels for thinned outimage (C) and the pixels for partial images (A, B) as mutually differentimaging frames. Accordingly, exposure is carried after the pixelelements of the pixel region 121 are reset. Exposure control and drivecontrol of pixel elements until being read next can be switched eachimaging frame and, therefore, the relevant control can be extremelysimplified.

In addition, the timing control circuit unit 150 selects a lowresolution reading mode on the entire image by thinning out reading anda high resolution reading mode by partial image reading based on controlby the system control circuit unit 160. At that occasion, the lowresolution reading mode on the entire image by thinning out reading andthe high resolution reading mode by partial image reading are differentin horizontal drive pulse and vertical drive pulse. Accordingly, thedriving timing of the sensor unit (imaging device) 120, the resolutionprocessing of the signal processing circuit unit 130 and the recordedpixel number recorded and processed in the recording and transmittingunit 140 are required to be changed for each reading mode. Thesecontrols are carried out corresponding with each reading mode by thesystem control circuit unit 160.

In addition, according to the reading modes, control is carried out sothat sensitivity of the sensor unit (imaging device) 120 is different.Specifically, the system control circuit unit 160 controls diaphragm(not illustrated in the drawing) of the optical unit 110. In addition,as another method, it is also considered that the gain of an amplifyingcircuit (amplifier) inside the sensor unit (imaging device) 120 ischanged to increase by a control pulse from the timing control circuitunit 150 so as to obtain a proper signal.

Next, the example of the embodied image of the present inventionillustrated in FIG. 2 will be described for easier understanding in thepixel level of the pixel region 121.

FIG. 3, FIG. 4 and FIG. 5 are schematic diagrams of the pixel region 121illustrating an example of an embodied image by the imaging devicerelated to the embodiment of the present invention. In FIG. 3, FIG. 4and FIG. 5, one pixel element (unit pixel element) 121 a is illustratedby a square. In FIG. 3, FIG. 4 and FIG. 5, a square (▪) painted withblack color specifies a pixel for thinned out image and a blank square(□) specifies a pixel for partial image.

In the example illustrated in FIG. 3, a pixel for thinned out image inthe horizontal direction and the vertical direction is treated as apoint. By reading such a pixel for thinned out image, the drivingfrequency can be made to be the lowest frequency and enables powersaving and reduction of the memory capacity of the signal processingcircuit unit 130. In addition, influence to resolution of a partialimage can be made small to such a level that deterioration due to thepixel for thinned out image can be ignored. An example of a circuitdiagram of an optimum unit pixel for the example illustrated in FIG. 3is illustrated in FIG. 6.

FIG. 6 is a diagram illustrating an example of a circuit in a unit pixelelement of a pixel region enabling random access. To a unit pixelelement 121 a illustrated in FIG. 6, a photodiode PD being aphotoelectric conversion unit, a transfer switch MTX for controlling andtransferring a signal charge of a photodiode PD to the gate portion of apixel amplifier MSFM (floating diffusion) and a transfer switch MVX areconnected. By controlling and transferring horizontal selection on therelevant pixel element with the transfer switch MTX and verticalselection on the relevant pixel element with the transfer switch MVX,random access to a pixel element becomes feasible. A residual charge ofthe photodiode PD is removed by bringing the transfer switch MTX, thetransfer switch MVX and a reset switch MRES into conduction at the sametime. A reset signal after reset of the gate portion of the pixelamplifier MSFM or a signal charge from the photodiode PD is amplified bythe pixel amplifier MSFM by controlling and bringing a select switchMSEL into conduction and is output to a vertical signal line Vh. Acurrent source switch MRV of the pixel amplifier MSFM is providedoutside the imaging region of a pixel element. Dispersion in the gateportion and the pixel amplifier MSFM is removed to attain low noise bycarrying out difference between the reset signal and the signal chargewith a CDS circuit unit (not illustrated in the drawing) in thesubsequent stage. Here, in FIG. 6, control pulses φSEL and φTX may sharea common control line.

In addition, the example illustrated in FIG. 4 illustrates the casewhere the pixel for thinned out image is provided on the row unit of thepixel region 121. In the example illustrated in FIG. 4, each pixelelement is controlled on the row unit and therefore will naturally carryout exposure on the row unit. In addition, the present example iseffective in the case where horizontal resolution of a thinned out imageis regarded significant. If in the present example, the pixel forthinned out image is utilized as a point pixel element as in FIG. 3,signals are selected and output by a horizontal scanning circuit unit ofthe sensor unit (imaging device) 120 or a pixel element read from thesensor unit (imaging device) 120 as in FIG. 3 and utilized from memoryof the signal processing circuit unit 130 can be selected. FIG. 7illustrates an example of a circuit diagram of an optimum unit pixelelement for the example illustrated in FIG. 4.

FIG. 7 is a diagram illustrating an example of a circuit in a unit pixelelement of a pixel region. In the unit pixel element 121 a illustratedin FIG. 7, one photodiode PD comprises one pixel amplifier MSFM.However, in that case, random access scanning of a pixel element is notfeasible but the gist of the present invention will not be spoiled.

In addition, another example of a circuit in the pixel region 121 isillustrated in FIG. 8. As illustrated in FIG. 8, one pixel amplifierMSFM can comprise a plurality of photodiodes PD. Specifically, in FIG.8, a plurality of photodiodes PD, a plurality of transfer switches MYXfor horizontal selection and one reset switch MRES are arranged for onepixel amplifier MSFM. Configuring as illustrated in FIG. 8, areas of thetransfer switch MVX for vertical selection for one photodiode and of thepixel amplifier MSFM become small and consequently there is an effect toimprove the aperture ratio of the photodiode.

The example illustrated in FIG. 5 is an example wherein only a pointpixel signal is utilized and the other signals are not utilized as athinned out image in pixel elements on the column and row related to thepixel for thinned out image. The circuits illustrated in FIG. 7 and FIG.8 will become an example of a circuit diagram of an optimum pixel regionfor the example illustrated in FIG. 5.

As a representative specific embodiment of the present invention to bedescribed below, an imaging device with the example illustrated in FIG.5 as an assumption will be described. Here, as a specific embodiment ofthe present invention, a mode applied to an imaging device with theexample illustrated in FIG. 3 or the example illustrated in FIG. 4 as anassumption will be naturally included in the present invention.

FIG. 9 is a diagram illustrating an example of a schematic configurationof a sensor unit (imaging device) 120 of an imaging device 100 relatedto an embodiment of the present invention. As illustrated in FIG. 9, thesensor unit (imaging device) 120 comprises a pixel region 121, ahorizontal shift register 122 for scanning the pixel region 121 in thehorizontal direction (row direction) and a vertical shift register 123for scanning the pixel region 121 in the vertical direction (columndirection). The pixel region 121 comprises a plurality of unit pixelelements (121 a) in a two-dimensional matrix and images the incidentlight of an object as an image. In an example illustrated in FIG. 9, anexample wherein the pixel region 121 comprises unit pixel elements of 32rows×48 columns is illustrated for making description understandable.

The horizontal shift register 122 and the vertical shift register 123are configured so that the method for scanning can be changed accordingto an image to be read based on control by the system control circuitunit 160 (see FIG. 1) through the timing control circuit unit 150 (seeFIG. 1). That is, the horizontal shift register 122 and the verticalshift register 123 comprise a “reading unit” for thinning out a pixelelement from the pixel region 121, reading a thinned out image in lowresolution and reading a partial image in resolution higher than thethinned out image from a partial region of the pixel region 121.Thereby, low resolution reading for reading a pixel signal only of apixel element 1213 for thinned out image at a predetermined thinning-outrate and high resolution reading for reading a pixel signal of a firstpixel element 1211 for partial image and a second pixel element 1212 forpartial image are feasible.

In addition, as illustrated in FIG. 9, the relevant reading unit readsthe thinned out image and the partial image from mutually differentpixel elements in the pixel elements of the pixel region 121 and readsthe thinned out image and the partial image as different imaging frames.

In addition, in the example illustrated in FIG. 9, as the partial regionof the pixel region 121 reading the partial image in high resolution,two partial regions are illustrated but the relevant partial region canbe provided only one in the pixel region 121. In addition, the three ormore relevant partial regions can be provided in the pixel region 121.

Next, a method of driving the horizontal shift register 122 and thevertical shift register 123 being the reading unit of this sensor unit(imaging device) 120 will be described. Here, the reading unit thins outpixel elements from the pixel region 121 in an arbitrary cycle and readsa thinned out image and reads the partial image in high resolution fromthe above described thinned out pixel elements (pixel elements besidesthe pixel elements read for the thinned out image) of the pixel region121. And, in the case of the present embodiment, a thinning-out ratewhen a pixel signal of the pixel element 1213 for thinned out image isread in low resolution is set to ¼ pixel element.

FIG. 10 is a timing chart illustrating an example of a method of drivingan imaging device 100 related to an embodiment of the present invention.Specifically, FIG. 10 illustrates timing for reading a pixel signal ofthe pixel element on each row in the sensor unit (imaging device) 120 ofthe imaging device 100. In addition, in FIG. 10, rows are read whenpulses are in High periods.

At first, in the case of reading the pixel signal of the pixel element1213 for thinned out image in low resolution illustrated in FIG. 9, thevertical shift register 123 reads the row 1 and, thereafter, reads everyfour rows such as the row 5, the row 9, the row 13, the row 17, the row21, the row 25 and the row 29. Here, although not illustrated in FIG.10, for driving the horizontal shift register 122 on each row, thecolumn 1 is read and, thereafter, thinning out and reading every fourcolumns such as the column 5, the column 9, . . . the column 45 isperformed.

Subsequently, in order to read the pixel signal of the pixel element1211 for first partial image in high resolution, the vertical shiftregister 123 is reset at first and the processing is returned to thehead row. And, if the region for the first partial image in highresolution is a region starting from the row 2 as illustrated in FIG. 9,the vertical shift register 123 reads the row 2 and, thereafter, readsthe row 3 and the row 4, next skips the row 5 and reads the row 6, therow 7 and the row 8. And, next the register skips the row 9 and readsthe row 10 and the row 11 to read the pixel signal of the pixel elementof a first partial image region 1211 in high resolution. That is, thevertical shift register 123 does not read the relevant pixel signals forthe rows having undergone reading the pixel signal of the pixel element1213 for thinned out image in low resolution such as the row 1, the row5 and the row 9 but reads the other necessary rows

And, after the previous rows for necessary reading, that is, up to therow 11 in the present example are read, the vertical shift register 123is reset to return to the head row and reads the pixel signal of thepixel element 1212 for second partial image in high resolution.

For reading the pixel element 1212 for second partial image in highresolution, reading the pixel signal is not carried out on the rowhaving undergone reading the pixel element 1213 for thinned out image inlow resolution likewise reading the pixel element 1211 for first partialimage in high resolution. Specifically, as for reading the pixel element1212 for second partial image in high resolution, the vertical shiftregister 123 is driven so as to read the row 18 to the row 20, the row22 to the row 24, the row 26 and the row 27 in the present example.

Here, occasionally, in reading the first partial image and the secondpartial image in high resolution, the problem of discontinuity of imagesby skipping reading of the read rows of the pixel element 1213 forthinned out image is also considered to occur. In that case, the signalprocessing circuit unit 130 (see FIG. 1) in the subsequent stage can bearranged to carry out complementary processing on the skipped and notread pixel element 1213 for thinned out image from the reading row inthe partial images in upper and lower high resolution.

In addition, as for a method of driving the horizontal shift register122 in the pixel element 1211 for first partial image and the pixelelement 1212 for second partial image in high resolution, any of twomethods to be described below can be used.

The first one is a driving method by reading only necessary columnsother than the columns undergoing reading of thinned out images in lowresolution, that is, the column 1, the column 5, the column 9, . . . ,the column 45. This driving method is a driving method in the caseillustrated in FIG. 9. At that time, when discontinuity of images due toskipped reading of the read columns of the thinned our images gives riseto a problem, the signal processing circuit unit 130 in the subsequentstage can carry out complementary processing likewise the case of therows.

The second one is a driving method wherein the horizontal shift register122 reads all columns. In that case, while one in four rows is not read,columns are all read. Therefore, the aspect ratio of the imaged imagewill be changed. Accordingly, the signal processing circuit unit 130 inthe subsequent stage also carries out complementary processing thereon.

An accumulation period of each pixel element in the drive of the sensorunit (imaging device) 120 related to the present embodiment will be asfollows. At first, the maximum accumulation period is a period fromreading of row in the previous frame to reading in the next frame. Forexample, as specified by an arrow in FIG. 10, the row 1 covers fromreading of the previous frame to reading of the next frame. During thatperiod, while reading of two frames of the partial image in highresolution is carried out in another row, the accumulation operation isgoing on in the row 1.

In the case where an accumulation period shorter than that maximumaccumulation period is desired to be set, a pulse for resettingaccumulation can be input from the timing control circuit unit 150 (seeFIG. 1) with arbitrary timing after completion of reading the previousframe. FIG. 11 illustrates such a manner.

FIG. 11 is a timing chart illustrating an example of input timing of areset pulse determining setting of an accumulation period of a pixelelement in a row 1. The case illustrated in FIG. 11A is the case wherethe accumulation time is maximum and is an example wherein a reset pulseis input immediately after previous frame reading to carry out resettingto start the accumulation operation and accumulation goes on untilreading the next frame. FIG. 11B illustrates an example wherein thereset pulse is input in the middle of reading and, therefore, thesubstantial accumulation period is shortened from after the completionof the reset operation by the relevant reset pulse to reading of thenext frame.

Frequently, there is the case where proper exposure of a thinned outimage in low resolution is not the same as proper exposure of a partialimage in high resolution.

For example, when the entire scenery of a town is read as a thinned outimage in low resolution and people passing in the shadow of a buildingare simultaneously read as a partial image in high resolution, theoutput level of the portion in the shadow of the building will becomelow. Thus, in the case of a situation with proper exposure beingdifferent for each read region, the embodiments of the present inventioncarry out the following two operations individually or in a mixedmanner.

The first one differently controls accumulation time in each imagingframe of the thinned out image in low resolution and the partial imagein high resolution. As described previously, in the present embodiment,the pixel element 1213 for thinned out image in low resolution isdifferent from the pixel elements 1211 and 1212 for partial image inhigh resolution. Accordingly, even if the row for reading the thinnedout image is reset with timing illustrated in FIG. 11B to shorten theaccumulation period, the accumulation periods of the first partial imageand the second partial image in high resolution will not be influencedbut exposure control on each image is independently feasible.Accordingly, in the present embodiment, for example, the system controlcircuit unit 160 (see FIG. 1) being a control unit controls exposure ofthe thinned out image in low resolution and the partial image in highresolution independently.

The second one is to change the gain of the reading amplifier (forexample, the pixel amplifier MSFM illustrated in FIGS. 6 to 8) in eachimaging frame for the thinned out image in low resolution and thepartial image in high resolution. In the case of this method, forexample, when reading of the thinned out image in low resolution is overand the vertical shift register 123 is reset to return to the head ofthe rows, setting on the gain of the reading amplifier is simultaneouslychanged to start reading of the next partial image in high resolution.

If the same pixel element is used for the pixel element 1213 for thinnedout image in low resolution and the pixel elements 1211 and 1212 forpartial image in high resolution, the system has to comprise twoamplifiers, that is, one for thinned out image and one for partialimage. Moreover, in that case, if setting of gain is the same, eachamplifier will have to comprise a complimentary circuit unit in highaccuracy so as to equalize outputs.

However, the imaging device related to the present embodiment isprovided with the pixel element 1213 for thinned out image in lowresolution and the pixel elements 1211 and 1212 for partial image inhigh resolution each independently and therefore can comprise oneamplifier. Accordingly, complexity in the system can be avoided. Here,in that case, as an advantage of controlling the output level with gain,capability of imaging a moving subject with little shaking is pointedout.

In addition, in FIG. 10, driving frequencies of reading of the thinnedout image in low resolution and of reading of the partial image in highresolution are illustrated on the same level. However, a mode where adriving frequency for reading each image is made different for eachframe can also be applied to the imaging device of the presentembodiment. That is, in the present embodiment, the horizontal shiftregister 122 and the vertical shift register 123, for example, carriesout reading with different driving frequencies for reading the thinnedout image and for reading the partial image.

FIG. 12 illustrates an embodiment of the present invention and is atiming chart illustrating an example of changing driving frequencies forreading the thinned out image in low resolution and for reading thepartial image in high resolution. The example illustrated in FIG. 12 isspecifically an example wherein the driving frequency for reading thepartial image in high resolution is twice larger than the drivingfrequency for reading the thinned out image in low resolution. Thereby,in addition to reading of the relevant first and second partial images,reading of the third and the fourth partial images can be further addedat the same period as the period for reading the first and the secondpartial images in high resolutions illustrated in FIG. 11.

Here, the present embodiment comprises pixel elements in the pixelregion 121 illustrated in FIG. 9 in 32 rows×48 columns and with athinning-out rate of ¼ pixel element but will not be limited hereto fordesigning an actual pixel region 121. In addition, also on the regionfor reading an image, in the present embodiment, regions of the pixelelement 1213 for thinned out image in low resolution and the pixelelements 1211 and 1212 for partial image in high resolution have beendescribed but will not actually be limited to this combination.Moreover, in order to simplify description on the driving frequency atthe occasion of reading each image, in the example illustrated in FIG.12, the driving frequency for reading the partial image in highresolution is uniformly twice larger than the driving frequency forreading the thinned out image in low resolution but will not be limitedto the twice larger frequency. In addition, the case where the drivingfrequency is different for reading of each image is applicable.

The imaging device 100 of the present embodiment reads the thinned outimage in low resolution and the partial image in high resolution frommutually different pixel elements and reads the thinned out image andthe partial image as different imaging frames. According to suchconfiguration, complexity in reading the image in low resolution andreading the image in high resolution is eliminated and decrease in framerate can be prevented.

Moreover, the imaging device 100 of the present embodiment can read aplurality of partial images because the driving frequencies for thethinned out image in low resolution and for the partial image in highresolution are different.

The units in FIG. 1 included in the imaging device 100 related to theabove described present embodiment and the timing charts in FIGS. 10 to12 illustrating the driving methods for the imaging device 100 can berealized by causing the program stored in RAM or ROM of a computer tooperate. This program and a computer-readable storage medium storing therelevant program are included in the present invention.

Specifically, the above described program is stored in a storage mediumsuch as a CD-ROM and otherwise provided to a computer through varioustypes of transfer media. As the storage medium for storing the abovedescribed program, media other than a CD-ROM such as a flexible disk, ahard disk, a magnetic tape, a magnet optical disk, a nonvolatile memorycard can be used. On the other hand, as a transfer medium of the abovedescribed program, a communication medium in a computer network (LAN,WAN such as the Internet, wireless communication network and the like)system for transferring and supplying program information as a carrierwave can be used. In addition, the communication medium at that occasioncan include a wired line such as an optical fiber and a wireless line.

In addition, not only the case where the function of the imaging device100 related to the present embodiment is realized by causing a computerto execute the supplied program, but also the case as described belowcan be considered.

One thereof is the case where the function of the imaging device 100related to the present embodiment is realized by cooperation of theprogram and an OS (operating system) or another application software andthe like in operation in a computer. The other one is the case where thefunction of the imaging device 100 related to the present embodiment isrealized by causing a function expanding board and a function expandingunit of the computer to carry out all or a part of processing of thesupplied program. The program in such cases as described above isincluded in the present invention.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2007-055769, filed Mar. 6, 2007, which is hereby incorporated byreference herein in its entirety.

1. An imaging device comprising: a pixel region that includes aplurality of pixel elements for imaging an object based on an incidentlight; and a reading unit for reading out a thinned out image at a lowresolution by thinning out a pixel element from the pixel region, andfor reading out a partial image at a higher resolution than the lowresolution of the thinned out image, the reading unit reading out thepartial image from a partial region of the pixel region, wherein thereading unit reads out the thinned out image in a first frame from afirst set of the plurality of pixel elements and reads out the partialimage in a second frame from a second set of the plurality of pixelelements excluding the first set of the plurality of pixel elements, andwherein the first and second frames are consecutive frames.
 2. Theimaging device according to claim 1, wherein the partial region is oneof a plurality of partial regions from which the partial image is to beread out, the plurality of partial regions being provided in the pixelregion.
 3. The imaging device according to claim 1, wherein the readingunit reads out the thinned out image by thinning out the pixel elementat an arbitrary frequency from the pixel region, and reads out thepartial image from the thinned out pixel element.
 4. The imaging deviceaccording to claim 1, further comprising a control unit for controllingindependently exposures for the thinned out image and the partial image.5. The imaging device according to claim 1, wherein the reading unitperforms the reading out of the thinned out image and the reading out ofthe partial image at different driving frequencies.
 6. A method fordriving an imaging device that includes a pixel region with a pluralityof pixel elements, for imaging an object based on an incident light, themethod comprising: reading out a thinned out image at a low resolutionby thinning out a pixel element from the pixel region; and reading out apartial image from a partial region of the pixel region at a higherresolution than the low resolution of the thinned out image, wherein thethinned out image includes signals read out from a first set of theplurality of pixel elements, and the partial image includes signals readout from a second set of the plurality of pixel elements excluding thefirst set of the plurality of pixel elements, and wherein the thinnedout image and the partial image are read out respectively from differentimaging frames.
 7. A reading unit comprising: a pixel region thatincludes a plurality of pixel elements, for imaging an object based onan incident light; and a reading unit for reading out a thinned outimage at a low resolution by thinning out a pixel element from the pixelregion, and for reading out a partial image at a higher resolution thanthe low resolution of the thinned out image, the partial image beingread out from a partial region of the pixel region, wherein the readingunit reads out the thinned out image in a first frame from a first setof the plurality of pixel elements, and reads out the partial image in asecond frame from a second set of the plurality of pixel elementsexcluding the first set of the plurality of pixel elements, and whereinthe first and the second frames are consecutive frames.